Process of and apparatus for clarifying liquids



' Dec. 28, 1937. J. J. sElP 2,103,828

v PROCESS OF AND APPARATUS FOR CLARIFYING LIQUIDS Ovrigi-nal Filed Deo. 8, 1932 L/Quolz 7 s/ uoeE our 1 SMC/Wm d John Jisei Patented Dec. 28, 1937 raocass or AND APPARATUS Foa cLAm-4 me Llomns John' J. serp', Allentown, ra. l

Application December 8, 1932. Serial No. 646,346 Renewed August 26, 1937 'z claims.- (cl. 21o- 55) This invention relates toprocess of and apparatus for clarifying liquids; and it comprises a process and apparatus suitable for clarifying liquids from suspended solids, such as areen- 5 countered in the defecation of cane and beet sugar juices, for example; the said process comprises introducing a stream of liquid to be clarified into a stilling zone of large volume, passing said liquid downwardly through al plurality of peripheral l0 discharge zones, usuallyv of increasing cross sectional area downwardly, passing portions of said liquid upwardly through a plurality of central clarifying zones, usually of increasing depth from' zone to zone downwardly, to centrally located clear liquor discharges and mechanically sweeping precipitated solids from beneath said dis.- charge and said clarifying zones; the said apparatus comprises a tank, usually cylindrical in shape, an inlet `for liquids containing suspended.A

matter at the top of said tank, a plurality oi' bell shaped members defining an upper stilling zone, a plurality of 'peripheral discharge zones, usually of increasing cross sectional area downwardly, and a' plurality of central clarifying zones, at least one of said'bell shaped members usually being provided with a restricted mouth, thereby producing` an adjacent discharge zone of increasing crosssection downwardly, means for withdrawing clearliquor from said clarify- 3.0 ing zones and mechanicalmeans for sweeping solids from the tops of said bell shaped members into said discharge zones at the bottom of said tank; all as more fully hereinafter set vforth and as claimed.

3;, Multiple tray clariiiers have been known in the A art for 20 years or morev During this period a large number of diierentdesigns have been proposed. One of the earliest types proposed was a so-called counter-flow type employing 40 apluralityof dished trays each provided with a.4

solids precir'iitatedY on. the traysare propelled along1 their surfaces in a radial direction towards the clear' liquor-exits The trays are provided 55 with at least one depending flange, the lclear More recently different types Y' exits being vlocated beneath the trays. The

liquor discharges usually being located adjacent to these anges. l l

It has been urged that the parallel ow principle is inherently superior tothat ofthe counterflow. It has been argued that the propulsion of 5 the solids counter tothe flow ci?y the liquid unavoidably tends to cause the resuspension of the solids. I have found, however, that this is not necessarily true.

-I have' found that, if the `velocity of the liquid 10 ilowing counter-to the propulsion vof the solids is made suicientlyl small, the tendency for resuspension of the solids is largely eliminated if not entirely overcome. I have found that the easiest method of accomplishing this desired re- 16 duction in velocity is to employ a peripheral ,dis-

of the openings, assuming, the same distance between trays and flanges. In a 20 foot clarifier I have found that the ratio of rates may be made )of the order of 10 to 1 or thereabouts.

. While the velocity of'fiow in the counter-how clariflers of the prior art is sumcient to obtain lan appreciable, and sometimes detrimental v amount of resuspension of sediment, I have found .-that the velocities of ilow occurring at the entry of the clarifying zones in my improved clarier are suillciently low as to'provide a substanto tially undisturbed/"discharge of sediment. even though this discharge-may be counter to the flow of liquid. Thus, I have eliminated the one 'disadvantage of prior art counter-flow equipments while `retaining all the inherent adm-46 tages thereof.

In all types of clariers employing a plurality of trays the bulk of the sediment is deposited on the trays close to the entry of the clarifying lsiones.

In the counter-dow type of clarifier this sediment .60

is removed by moving it towards vthe nearest exits, namely those -through which it entered the clarifying zones. The sediment is thus, at least theoretically. moved the' shortest distance possible and most directly from its point of deposit is to the smdge. exit. ,1ncontrast to this, in the parallel-110W equipment, the sediment deposited close vto the entrance of the clarifying zones is propelled across substantially the entire width of f the 'trays towards the openings most remote fromv the points of deposit. This results ina considerable'accumulationof lsediment within the clarifying-zones.

A vsecond -inherent advantage in the counter'- f flow clarlers is due to the fact that there is usually a greater distance between the clear liquorI discharges and the entrancesto the clarifying zones than ,in the parallel flow clarlilers, due to the necessity of .having both central and pei -ripheralopenings in the trays of the latter type.

This feature provides a'longer time and a greater opportunity for the solids to precipitateV without .being carried over into the clear liquor, `In'the prior types; of co-unter-flowclariilers theginherent advantages of this; type were more than counters balanced by the'diiculties arising from resus- A pension 0I. the deposited sediment.

.My new design 'of counter-flow clarier pos'- sesses all the advantages inherent-in a'counterff In addition it possesses several adflow type. vantages characteristic of the new design. I

'haveffound, for example, that, the distances from g' the entrances of the clarifying zones to the clear liquor'discharges can be made even greater in my new type than in the prior type of counter-flow clarifier. This is due to the fact that, when a central down-.take is employed, this must necessarlly have a width in the direction of the radius 'of vseveraltimes that employed in the peripheral discharge zones used in the present invention.. In my design the distance between the upper tray flange and the tank wall can bemade Voi .the

This is in contrast to order of about 2 inches. a radius -of at least about 18 inches for the central down-take of a counter-flow clarifier ofthe prior art. This represents a gain of. approximately 16 vinches in the distance between the entrance to 'the clarifying zones and the clear liquor, draw-offs.

As mentioned previously, the great majorityof solids deposit on the trays of a clarifier close to.

- theentrance of the clarifying zones. In the prior Avo art counter-now type of clarier. this precipitation took place within a comparatively small areaadjacent to the central down-take. The depthof. And `during the propulsion of the solids to the discharge zone, the solids converged centrally, thus piling up to a considerable depth before finally being pushed 01T the central edge of the tray. In

the deposit was therefore rather large.

mydesign the tray area upon 4which the bulk of solids precipitate is from 8 to IO-'times as large.- MyA new design provides `the largest possible settlingarea. Moreover, during the propulsion of the'solids.` toward the peripheral discharge of. my trays the settling area increases and thereis no tendency for the solids to heap up. It is of course obvious that the greater the depth of solids at the entrance to the clarifying zones, the greater the tendency for resuspension. In my design, this tendency is substantially eliminated, due not only to the decreased velocity of flow ofsthe liquidsbut' also to the smaller piling up of solids at this polnt.

During the operation of my new clarifier I have found still other advantages in my new design, which were probably masked or overcome by the resuspension of' solids. in the prior counterilow type. I have found that there is a somewhat smaller. loss of pH during the clarication of sugar juices for example, that the muds have an 2,103,828 I improved illtrability and-'that-jthe locs have ing the orificesvv of the discharge rates.-

less tendency to break up. A clarifier of my new design has an appreciably' higher capacity than that of previous types. I attribute these advanfv rtages to the shorter timev of.- contact .of the muds with 'the liquid whichv is -beingA clarified. The

muds are"propelle'd quickly and expeditiously by' i thejshortest and most direct route to the sludge draw-loi. y There isless recontax'ninationv of muds through successive recirculation;- The clearliquor discharge collectors' are locatedin 4 a quietzone,

at the greatest possible distance'i'rom' the intake v andl consequently free from' all disturbing influer'ices. .This minimizes the :injurious counter, andeddy currents produced in the'prior counterilow' cIarier.' Bytheuse of special collecting -nipples -mounted in the clear liquor collector I j" ain enabled to Iproducea weir eiect providing.a, quiet, .undisturbed drawing' oi. ofclear liquor.

.without the Asuction eiect usually encountered in a pipe'draw'off. Thispreventsfanysuspended" drawnup'wardly by 'dis-,

material from being charge eddies.`

Otherv advantagesfof/ my' new design Awill` liecome evident in the further, discussiomduring whichreferencelwill ybe madefto the accompany-- ingdrawing lwhich shows, mo're'or'l less diagrammatically, an assembla'geof apparatus elements` within the purview of vmy invention. and'fuseful in theprocessof my invention.' In this'showing 3o: Fig -1 is a Vrtical central section of one form ,0f11u/clarifier,.4

Fig. 2 is a plan View oi.' onelfo'rni'of` clear liquor' l discharge collector, while i.

Fig. 3 is a vertical section `offa draw-olf nipple 1 advantageously employedin said collector..

In the severaltlgurS-various structural' l'elles v ments are 'represented by` thesamef ,reference clear liquor draw-offs 4, la, 4b etc.,' and 4with -a sludge outlet 5 Supported-within1-the tank 'I by brackets v6 orv other means` are a1series-"of belled or Vcrowned trays 1, 1aetc.These trays are providedwith depending peripheral flanges trays above vand below, clarifying zones 9, 9a etc.

50 I, 8a etc., which form, within the confines of the The flanges l, 8a etc., also. deilne'v'erti'cal dis- Y charge zones I0, Ia etc., between themselves and.

the wall of the tank. The upper traylis placed at some distance below the liquid `level 4I I inorder to provide a stilling zone I2 of subst'antialvolume.

Beneath each of the trays at 4thece'n'ter`r there are mountedcollecting ringsfa etc`.,j con necd with the clear neuer. drawqrrs; These' 'rings are' provided kwith ,collecting nipples la; i

a section being' shown-in' Eig.f3. -Thesle'nipples are threaded into holes 2).iifiji7heV41 Upper surfaces of the collecting rings.j` The il-Dper walls ofthe nipples are tapered 'at ytheir orifices i6 (1"lg..3)l ln order-to prevent collection of'sediment vat this point. The. threaded" portion of the nipples provides a convenient method yof level' nipples to provide equal A. central shaft Vll is provided for carrying the sweeps orscraper arms I8, lla etc. The shaft is rotated by conventional .gearing andl source of power 'not shown. Rotationfis at a very slow `amasar;

speed, usually not over 20 revolutions per minute as a maximum. The scraper arms aresupported by ties.,|9 and turnbuckles 20. The sweeps are provided with rabbles orfflights 2l which serve to move the precipitated solids over the surfaces of the trays and towards the peripheral discharge zones.

The operation of my apparatus isbelieved obvious from Fig. 1 which shows, on its right hand side, thedistribution of solids in the clarifier during operation. The liquid to be clarified ows in at intakes 2, several of which may be located around the periphery of the tank. The liquid enters the stilling zone I2 and passes down the peripheral discharge passageway ill. Any solids deposited on tray 1 are also discharged through passageway l0, being propelled over to this'point by means of sweeps lloperated by shaft I'l. The bulk of the sludge falls directly downwards rthrough the successive discharge zones, I Ua, 10b

etc., which advantageously increase 'in cross section downwardly in vorder to provide larger discharge zonesas the quantity of precipitated solids increases in bulk.l A fraction of theliquid passing through discharge zone Il) enters into `the clarifying zone 9, passing through the entrance 22, as indicated by the arrow. This liquor passes into zone` 9 at an extremely slow rate due to arisesand finally 4passes out at the collecting The solids deposited on tray 1a arel ring I3. rabbled in a direction towards opening l22 and arel finally discharged into discharge zone Illa. The same process takes place in the successive trays beneath' 1a; the clarified liquids passing out of the vclarifying zones through the collecting rings and the solids precipitated within the clarifying z'cnes being passed into the discharge zones below.

At the lower discharge zones, the density of vsolids increases due to accretions from the sucwardly at the bottom; This providesl discharge zones of `increasing cross sectional area down wardly. In accordance with a copending application,4 Serial No. 633,520-, filed September 16, 1932,

A I usually incline or taper the lowest' flange 8d inwardly at the bottom, providing a discharge zone Ind of increasing crcss.sectional area downwardly. Also ih accordance with myacknowledged application I usually provi e. increasing dstances between the successive trays downwardly;

this producing clarifying zones of. increasing depth. Both the increased cross.- section ofthe ischarge zones and the greater depthsof the clarifying zones tend to overcome the difliculties introduced by the increased amounts of precipf: itated solids towards the bottom ofthe clarler.A

upper trays, due to the increased amount of solids which they are required to handle.

I usually allow aconsiderable depth of solids to build up on ,the floor of my clarier. I'his is to produce a sediment bed of gelatinous sludge through .which all lincoming solids and=`liquids must pass, thesludge bed forming a seal with the lowest tray and depending fiange.l The sludge bed provides an excellent lter or entangling mediumto trap any finely divided, suspended solids. When the depth of this sludge bed is correctly controlled, which may be accomplished by a series of sampling pipes at varying heights extending into the clarifying zone, for example, a consistently superior clear liquorA is produced. The effect is much like the seeping of Vwater through a bed of sand.

While I have described my invention in some detail various modifications can be made therein inthe case of .liquids having troublesome foaming characteristics-a peripheral foamlaunder may be provided. With some types of liquids it is possible to provide a clear liquor draw-oir in the upper stilling zone, usually centrally located. This stilling zone is advantageously made offisome depth in order to act as an equalizin'g chamber to accommodate variations in pumping rate of f the liquids, etc.` Otherwise such variations are likely to disturb the operationof the clarifier as af whole.'

For cleaningl the clarifier I may provide flush manholes in the various trays. In the case of large` capacity clariers it is sometimes advantageous toprovide a suilicient distance between the trays and the` wall of the ta'nk for -a boatswains chair and a man carrying'a hose to be lowered for cleaning purposes. In the case of a 20foot tank, for example, a distance of from 18 to, 24 inches may be provided at the periphery of the trays for this purpose. In this design the discharge Vzones are usually of suicient width to eliminate the necessity of stepping the trays inwardly from the top to the bottom of the tank;` that is the various discharge zones may be made of the same width.

In the caseof liquids causing difficulties by producing foam within the clarifying zones, I sometimesprovide small central openings in the trays below the top tray 1. These openings sur--` round the central 4shaft and are large enough 'Y to provide a discharge for foam at this point. vThis opening performs a second function, namely to prevent the piling up of sediment on the trays adjacent to the central shaft where it cannot be reached by the conventional type of Scrapers.

Due to the fact that, in my clarifier, the great bulk of the sediment is deposited adjacent to 4the openings 22, 22a etc., very little sediment finds its way to the center of the clarifying zones -ad- I jacent to the central shaft, Very little sediment is deposited at this point on all trays save the top Atray 'I. Clear liquor cantherefore be drawn on' frompracticallyany centrally located point of the clarifying zones. When I employ thecentrai openings vin the lower trays ras described I therefore usually 4mount the vcollecting rings with Ain the'clarifying zsnes about midway of their height.- The foams rise successively through the lower trays and finally-collectbeneath the top tray. From this point they may be withdrawn 'thrbugh la special collecting launder, usually in special scraper to remove sediment from the dead -space adjacent to the central shaft. take the form of a chain or a special plow blade.

My new design clarifiers, may be 'made to cover a great range of capacities. Both the heights of the tanks as well as their diameters may bevariedQgreatly. The prior art counter-now type of clarifier is greatly limited as to the number of trays which can be employed. When handling liquors containing a high percentage' of solids no more than about 4 trays can be employed and, even' in the case of a four tray clariiier, the bottom tray is capable of only a strictly limited discharge-of clear liquor. In my design, employing discharge zones of increasing cross section and clarifying zones of increasing depth downf" wardly, there is .no such limitation. Practically double the number oi'- trays canV be employed inthe new design. This fact greatly increases the ilexibilityoi design. For an increase in capacity the height` of the tank and its number of trays may be increased, or the diameter can be increased with use of the same number of trays. For a 20 foot clariiler I usually employ about 'I trays, the distances apartl varying from about 2 feet for the two top trays to 3 or '4 feet for the `distance from the bottom of the tank to lowest tray. The discharge zones may vary in width correspondingly, varying from about 2 inches to 24 inches at the lowest zone.

The flanges depending from the trays of my clariner can'be made vertical or they can be sloped inwardly or outwardly. An inwardly slop- An inwardly sloping `flange has Aother important'Y advantages vset out at. length in my acknowledged copending application.

- The trays of the present invention are formed of superimposed bell shaped members which dene a plurality of peripheral discharge zones and a plurality-of central clarifying zones. At least onel (usuany the 1owest) of these beu shaped members is provided with a constxicted mouth,

-thereby forming a peripheral discharge .zone o! increasing .cross sectional area downwardly and a clarifying zone of increasing cross sectional area upwardly.

clarifying zones,` it is possible to allow a considerable distance between the topof one tray and the depending 'ilange of the tray above without reducing the capacity of the clarier. Such a construction also lprovides suillcient room beneath the ilanges 8, la etc., for the clear liquor draw-` oifs. That is, these draw-offs may be run through the entrances 22 to the clarifying zones as shown in Fig. l. It is, of course, possibleto pass the clear liquor draw-oils through the flanges but the other construction oilers advantages. F

In one modication of my clariiler I employ a hollow tube in place of the shaft I1, using this tube as a clear liquor draw-oil. A series of staggered openingsin this tube are provided in each clarifying zone and the clear liquor runs downwardly through a stuillng box at the lowerend and into This mayV a clear liquor conduit. Collars are provided on the tube to close any desired portion of the staggered openings. These openings are made smaller in the lower clarifying zones to provide substantially equal rates oi discharge froml each zone. It is of course possible to employ a combination of several individual clear liquor draw-oils with a central tube which acts as a draw-oit for the remaining trays. .The central tube draw-of! is more suitable for handling the upper trays, while-the individual draw-oils are somewhat more satisfactory for the lower trays. v

While I have enumerated a number of varia- 'tions in designI which can be employed in my clariiier, there are numerous other modifications which will be immediately'evident to those skilled in the art and which are included within the scope of the following claims. 'I'hese modifications I consider within the purview of the present invention.

What I claim is:

1. In apparatus for separating solids from liquids, a tank provided with an inlet for liquids Acontaining suspended .matten a 'plurality of superimposed bell shapedmembers'closed at the top defining an upper stillingzone, a plurality of peripheral discharge zones and a plurality oi' central clarifying zones; means within said 'clarifying zones for removing clear liquor and means for withdrawing precipitated solids at the bottom of said tank; at least one of said bell shaped. members having a constricted mouth,

thereby forming a peripheral discharge zone of 'increasing cross sectional area downwardly.

said liquid downwardly through a plurality of peripheral discharge zones, passing portions of said liquid upwardly through peripheral openings and centrally into a plurality of central clarifying zones of increasing depth from zone to zone `downwardly to 4centrally located clear liquor draw-oils and' With-drawing precipitated solids from. beneath said discharge .and said clarifying v zones in a direction counter to the ilow of said liquid.1 I v Y 3. In the separation of solids from liquids, the process which comprises introducing a stream of liquid to be,- clariiled into a stilling zone, passing said liquid downwardly through a plurality of peripheral discharge lzones in series, passing portions oi said liquid upwardly through peripheral openings and centrally into a plurality of central clarifying zones to centrally locatedclear liquor draw-oils and with-drawing precipitated solids from'beneath said discharge and said clarifying zones in a direction counterv to the ilow of said liquids; -at least one of said clarifying zones being oi' increasing cross sectional areaupwardly and -process which comprises introducing a stream of liquid to be claried into a stilling zone, passing vsaid liquid downwardly through a.l peripheral discharge zone, passing a portion of said liquid upwardly through a peripheral opening into a central clarifying zone to a central clear liquor discharge, passing the remainder of said liquid, to-

fying zonedownwardly through a"l second-peripheral discharge zone of increasing 'cross sectional area downwardly, passing a portiorioi said revat least onel of said discharge zones being of gether withA solids precipitated within said clarithereby forming a clarifying zone of -increasing maining liquid upwardly through a second peripheral opening into a second central clarifying zone of increasing cross sectional area upwardly to a clear liq-uor discharge and withdrawing preycipitated solids from beneath said discharge and said clarifying zonesin a direction counter to the flow of said liquid.

5. In apparatus for separating solids from liquids, a tank, means for separating said tank into an upper stilling zone, a plurality of superimposed clarifying zones of increasing depth from zone to zone downwardly,-and a plurality of peripherai discharge zones; means for withdrawing clear liquor centrally located within said clarifying zones and means for discharging precipitated solids from said tank.

6. In apparatus for separating solids from liquids, a tank provided with an inlet for liquids containing suspended matter, a plurality of superimposed bell shaped members closed at the top defining an upper stilling zone, a plurality of peripheral discharge zones and a plurality of central clarifying zones; means within said clarifying zones for removing clear liquor and means for withdrawing precipitated solids at the bottom of said tank; the'lowest of said bell shaped members being provided with a constricted mouth,

cross sectional area upwardly.

'7. In an apparatus for clarifying liquors from suspended solids. a tank, a plurality of superimposed trays centrally mounted in said tank having diameters smaller than that of said tank and being provided with peripheral flanges depending close tothe tops of the next lower trays,

said trays being closed at the top being substantially horizontal but sloping slightly downwardly towards their periphery and defining a plurality of central clarifying zones and a peripheral discharge zone for solids, the spaces'left between said flanges and said trays providing thel sole entrance for liquor to be clarified into said clarifying zones, means for introducing liquor to be clarified into the tank above said traysrmeans for withdrawing clarified liquor mounted centrally at the upper part of said clarifying zones, means for mechanically propelling solids precipitated on said trays peripherally along the surface of said trays through said entrances and into said discharge zones in vcounter flow to the liquor passing through said entrances and means for withdrawing sludge from the bottom of said tank.

JOHN J. snm 

